CVE-2026-50053
HIGHDescription
A request attribute override vulnerability in Zimbra Collaboration Suite (ZCS) allows unauthenticated requests to /h/* to populate servlet attributes intended for trusted internal dispatch. RestFilter copies URL parameters specifying an authentication token, target account, target item and dispatch state into the request attributes consumed by the Classic Web Client. Combined with CVE-2026-10632 on ZCS 10.1.16, this allows an attacker to supply their own valid token and document identifiers and execute JavaScript in another user's signed-in browser session. ZCS 10.1.17 blocks that XSS chain by changing the document renderer, but retains the request attribute override.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 23% of all known CVEs.
References
Related Vulnerabilities
Other CWE-642 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2026-29146 | High | 7.5 | 8.8% | - | Fix |
| CVE-2019-9496 | High | 7.5 | 4.7% | - | Fix |
| CVE-2018-15382 | High | 8.6 | 1.3% | - | - |
| CVE-2017-0928 | Medium | 6.1 | 1.0% | - | - |
| CVE-2020-27872 | High | 8.8 | 0.9% | - | Fix |
| CVE-2023-0575 | High | 7.2 | 0.8% | - | Fix |
Common questions
How do I fix CVE-2026-50053?
No published fix for CVE-2026-50053 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2026-50053 being actively exploited?
Not that we know of. CVE-2026-50053 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.30% is the estimated probability that it will be exploited in the next 30 days. That is higher than 23% of all scored CVEs.
How severe is CVE-2026-50053?
CVE-2026-50053 has a CVSS v3 base score of 8.7, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-10-28.